1. Field of the Invention
The present invention relates to an input device having primary input means serving as a coordinate input unit and secondary input means having a plurality of push switch elements.
2. Description of the Related Art
Japanese Unexamined Patent Application Publication No. 2002-123363 is directed to an input device for use in, for example, portable telephones. The input device disclosed in this publication includes an electrostatic-capacitance or pressure-sensitive flat input unit 4, a cover sheet 7 formed on a surface of the flat input unit 4, and switch elements 11 used for a switch input operation (see FIGS. 2 and 7 of the publication).
In the above-noted publication, as recited in paragraph number [0022], the flat input unit 4 has a coordinate input capability, and has functions for inputting numbers and characters by pressing indicator keys 8 shown in FIG. 1 of this publication and for scrolling a view displayed on a display panel 3 by changing to a certain mode (see paragraph numbers [0030] to [0032], etc.).
When the switch elements 11 are pressed and turned on, for example, as recited in paragraph number [0043], only a press of the switch elements 11 is sensed while ignoring a coordinate input signal generated by the flat input unit 4. A press of the switch elements 11 serves as, for example, a “set” button.
Generally, the switch elements 11 are connected to separate signal lines, and these signal lines are connected to a switch position detector in a controller. When a switch signal is detected, the switch position detector determines which switch element 11 is turned on based on the signal line carrying the switch signal.
An input device to be incorporated in a compact electronic apparatus, e.g., a portable telephone, should also be small. Thus, the larger the number of switch elements 11 is, the more difficult it is to design the wiring of the signal lines corresponding to the switch elements 11 in the input device within a limited space.
It is also unavoidable to change the design of a controller for detecting switch signals when the number of switch elements 11 changes.
The switch signal lines individually provided for the switch elements 11 experience another problem in that noise is liable to occur.